Field of the Invention
The present technology relates to an imaging system and an imaging apparatus including analog-to-digital conversion circuits to convert analog signals into digital signals.
Description of the Related Art
According to the related art, an imaging apparatus is known to include pixels that are arranged in a matrix, perform photoelectric conversion, and output signals based on incident light, and to include column-parallel analog-to-digital circuits (hereafter, analog-to-digital circuit is referred to as an ADC (Analog Digital Converter), and the column-parallel ADC is referred to as the column ADC), which are provisioned in each pixel column, that perform AD conversion on the signal output from the pixels. A circuit unit in each column in the column ADC performs analog-to-digital conversion (hereafter, referred to as AD conversion) to convert the analog signals output from the pixels (hereafter, the “analog signal output from the pixels” is referred to as pixel signal) into digital signals.
Also, Japanese Patent Laid-Open No. 2004-134867 discloses an imaging apparatus including pixels that output a first pixel signal based on a first signal charge accumulated in at least one photoelectric conversion unit, and a second pixel signal based on a signal charge calculated from the first signal charge and a signal charge accumulated in another photoelectric conversion unit. According to this imaging apparatus, the viable signal range of signal values for the first pixel signal is narrower than the viable signal range of signal values for the second pixel signal.
Japanese Patent Laid-Open No. 2000-59687 discloses an imaging apparatus that includes pixels which include multiple photoelectric conversion units with different surface areas. When the same amount of light is illuminated on the multiple photoelectric conversion units, the photoelectric conversion units with larger surface areas produce larger signal charges as compared to the photoelectric conversion units with smaller surface areas. Thus, the viable signal range for pixel signals based on photoelectric conversion units with smaller surface areas is narrower than the viable signal range for pixel signals based on photoelectric conversion unit with larger surface areas.